This description will use the term “note” as a descriptor for currency, banknotes, barcode coupons and other documents that may be electronically scanned for recognition and validation.
There are numerous systems used in the note validation field. Several manufacturers have developed note validators that use similar basic validation techniques. These devices typically use optical methods and means to determine the type and authenticity of a note.
Usually, light from an LED is transmitted through, and in some devices, reflected from the note in question. A transport moves the note past individual photo detectors arranged perpendicular to the direction of travel of the note. The individual photodetectors detect the transmitted and reflected light from the note, and convert that light into electrical signals that a microprocessor samples and stores. The pattern of detected signals is then compared through an algorithm to representations of authentic notes stored, for example, in a database. Through these algorithms, a decision is made regarding the type and authenticity of the inserted note. Once validated, the note is typically transported to a secure storage box or stacker, integrated with the validator.
In the United States, notes of varying denominations are cut to the same width, 68 mm. Many other countries designs use notes of varying width, usually increasing the width of a note with increasing denomination. As an example, the European Union utilizes notes with widths ranging from 62 mm for the five Euro note to 85 mm for the five hundred Euro note. Thus, a validator must accommodate the range of widths of the inserted notes. This complicates the recognition process, as the smaller notes, if inserted in a wide channel, will be inconsistently positioned with respect to the sensors used to recognize and verify the notes.
Validators typically use between five and eight individual photodetector sensors for note recognition. This means that a small note in a wide channel will actually produce several different possible signals for collection by the validator depending on its position on entry into the validator. Since the smaller notes do not cover the entire channel, one or more sensors will be partially or completely uncovered, rendering data from this sensor(s) of little or no use in validation. The potential multiple variations of signals that can be generated by the same note are stored internally, using up valuable memory space, increasing the cost of a practical validator and/or reducing the number of different denominations that can be recognized. A note may also be inserted at an angle to the sensors, causing a skewed representation of the note to be scanned, and further potential signal variations on a note.
One method of addressing this problem is to use a mechanical device to automatically straighten and center the note before the validator passes it over the sensors. As an example, UNIVERAL BILL ACCEPTOR (UBA) manufactured by JAPAN CASH MACHINE, CO., LTD. uses this method in one of their products. When a note is inserted into the validator, it is drawn into a pre-scan area by drive wheels. A mechanical centering mechanism is then activated to center the note in the channel. When the note is centered, the bill transport starts transporting the note past the validation sensors. Bill centering channels act as guides to keep the note moving straight and aligned with the sensor system.
This method may have the advantage of aligning the note to the sensor system with repeatability for each insertion, ensuring that the sensors reliably read the same area of the note for each insertion of a particular denomination. Accordingly, this may reduce the amount of data needed for the stored representations of a particular valid note.
The drawbacks to this method are the time required to physically center the note, the additional parts for the mechanical centering system and the room required in the validator for the centering mechanism. It also may take additional time for such mechanism to physically center the note. The additional parts for centering the note add cost and complexity to an already complex mechanism for validating currency. Space for a validator in the typical vending machine or slot game is usually quite limited and the additional centering mechanism adds volume or uses space that might be used for additional validation sensors.
In another type of validation unit, for example, a VECTOR model manufactured by Valtech, Inc., the user must align the note to one edge of the validator to activate the unit. While this can promote correct positioning of the note, it requires the user to be informed of this method by signage, pictures or text before using the validator. Also, a note with a torn corner may not be accepted by a unit of this type if the missing corner is located where the edge detection sensor is located.